372 CHLOROPHYLL-GRANULES AND THE SUN'S RAYS. other hand, is forraed of a porous mass of reticular or scaffold-like strands, which may best be compared to a bath sponge. The holes and raeshes of this spongy colourless ground substance contains a green colouring matter, which is dissolved in an oily material, and clothes the continuous small spaces in the forra of a parietal layer. This green colouring raatter of the chlorophyU-granules, which has been called chlorophyll, is easily soluble in alcohol, ether, and chloroform. If green leaves are steeped in an alcohoHc solution, they become blanched in a short time, and the colouring matter passes entirely into the fiuid. The alcohol assuraes the beautiful green colour which the leaves formerly possessed, and the previously green leaves are now to be seen floating in the green alcohol. In transmitted Hght the solution appears a beautiful green; but when observed in reflected Ught it appears blood-red, and therefore the colouring matter displays a raarked fluorescence. If a fatty oil is added to the green-tinted alcohol, and the two are shaken up together, the green colour passes into the added medium, while in the alcohol a yellow substance reraains, which has been terraed xanthophyll. The chemical composition of chlorophyll is not yet so clearly understood as we could wish. It is asserted that it is possible to obtain chlorophyU in a crystallized form. The crystals obtained form green transparent rhomboids, which, when exposed to the light, slowly decompose again. This chlorophyll behaves like a weak acid; contrary to earlier belief, it is free from iron, but leaves behind alraost 2 per cent of ash, consisting of alkaHes, raagnesia, sorae calciura, phosphoric and sulphuric acids. The fact that the production of these crystals must be preceded by a series of long- continued operations, together with the fact that chlorophyll is extreraely delicate and easily decomposed, always allows us to suppose that the crystals raentioned are only a product of decoraposition, and do not belong to that chlorophyll which colours the chlorophyll-granules in Hving cells. It was previously thought that chlorophyll was a raixture of two colouring raatters, viz. a blue and a yellow, until later researches demonstrated that this supposition was unfounded, and that a false impression had been received through observation of the process of decoraposition. A characteristic absorption spectrura has been obtained for chlorophyU, which is especially useful in all cases where it is a question of demonstrating the presence of very small quantities of the colouring matter in any parts of the plant. With respect to this it is enough to say that the whole of the violet and blue and the ultra-violet rays are cut off frora the spectrum, and that it exhibits seven character¬ isticaUy distributed absorption-bands. It may be further reraarked here that after treating the chlorophyll with hydrochloric acid tiny crystals arise, which have been called hypochlorin. The results of all these researches have thrown but little light upon the part which chlorophyll plays in those processes which coraraence with the decoraposition of the absorbed carbonic acid in the chlorophyll-granules. Compared with the size of the whole mass, chlorophyll forms only an extremely small fraction of the granules it colours green, and when it is withdra-wn by the addition of alcohol, only the colour and not the size of the granules in question is found to be altered.